“Sound is vibrations propagating through a medium such as air. The detection of these vibrations is a mechanical sense akin to a sense of touch. In humans, this perception is executed by tiny hair fibres in the inner ear which detect the motion of a membrane which vibrates in response to changes in the pressure exerted by atmospheric particles within a range of 20 to 22000 Hz, with substantial variation between individuals.” (source)

Using Soundscapes: Boat Captains off the Coast of Canada:

“They used to get their position by echo whistling. They’d give a short whistle and estimate the distance from the shoreline by the returning echo. If the echo came back from both sides at the same time they’d know that they were in the middle of the channel. They could recognize different shorelines by the different echoes – a rocky cliff, for example, would give a clear distinctive echo, whereas a sandy beach would give a more prolonged echo. They could even pick up an echo from logs. Nowadays, if the radar (or GPS) breaks down, they have to put out an anchor. Their ears aren’t trained to listen their way through the fog.” (Schaefer)